For the first time, the Blu-ray (HD) edition of the films was released on the same date as the normal DVD.

Guest stars include George Takei and Rich Little as themselves. In addition, Gary Gygax has an appearance at the end of the credits, and the film is dedicated in honour of him. Gary Gygax is listed at a guest star as well.

Cubert and Dwight, along with two otherfriends, are playing a game of Dungeons & Dragons when Bender walks in on them, unable to comprehend what they are talking about when they discuss what they are imagining out loud. Since he only sees the kids sitting around a table playing a game, the kids realize that he was not built with an imagination, which makes Bender feel a bit insecure.

Bender complains to Fry, wondering if he has an imagination; Fry simply tells Bender that he won't know if he can imagine something until he tries. All of a sudden, the ship's engines run dry of dark matter and shut down, stranding the ship in a backwater region of space. Fortunately, Nibbler poops out just enough fuel to reach the nearest Mombil fuel station. As Leela refils the tank and complains about how expensive dark matter has become, costing $9.99 a ball, she is approached by Sal who mocks the ship, calling it ugly despite the terrible shape his own ship is in. Sal proudly states this is so because he is a five-time winner of the Space Demolition Derby, and that he will be entering. Angered, Leela decides to enter the ship to teach Sal a lesson.

Returning to the Planet Express building, the crew is informed that with tripling dark matter prices, Farnsworth has forbidden the wasting of fuel, swallowing the keys to the ship and going to bed. Still unable to contain her anger about being insulted by Sal, Leela insists that they must enter the derby, even if the ship gets totaled, and has Zoidberg retrieve the keys from the Professr's stomach with a magnet. The crew blasts off to the derby arena.

At the derby, Leela unleashes her rage and concentrates on Sal's ship while the other ships demolish each other. Soon only their two ships remain, both charging headlong into a surefire collision course with each other...

Deciding not to take any risks, Sal admits defeat and swerves out of the way of the charging Planet Express ship, crashing and granting Planet Express a solid win. Returning to the building, the crew attempts to cover up the damaged ship with a curtain and puts the keys back into Farnsworth's stomach in his sleep. However, when Farnsworth awakens, he decides to take the ship to the malt shop. Leela orders Zoidberg to distract him by juggling torches while balancing on a ball, but he falls and burns up the curtain, exposing the ship's damaged shape. Farnsworth, however, does not notice the damage, only growing concerned when he sees that someone has wasted half a ball of dark matter, so Leela assumes full responsibility.

Meanwhile, Bender tries to play D&D with the kids, but is still unable to get the hang of his imagination. After some encouragement from Dwight, who tells him to lose himself in the fantasy, Bender convinces himself to believe that he is a medieval knight. Producing the image in his head, Bender proudly claims that he imagined something, and names his D&D character "Titanius Anglesmith, Fancy Man of Cornwood."

Leela is brought into the conference room to be punished over her severe anger issues. Because Zoidberg tattled on Leela to Farnsworth about all the things she did by letting her anger get the best of her, he is rewarded while Leela is forced to wear a shock collar, which activates every time she has a violent thought, swears, or has sexual perversions. Leela grows furious with Zoidberg and gets her revenge by electrocuting him, using Bender as a conductor.

Leela is informed that her collar can only be removed if she can convince Zoidberg that she has controlled her anger. After growing frustrated when Zoidberg tries to remove her skull to alleviate her anger, as well as spraying her with his empathy bladder, she declares that the source of her anger is her intense hatred of Zoidberg; Zoidberg, however, determines that it is truly rooted within her relationship with her parents (even though he is really thinking about his own parents). Zoidberg suggests that they both go visit them for dinner to work things out.

Meanwhile, Bender delves deeper and deeper into his own imagination to the extent that he be called "Titanius Anglesmith" everywhere. Disturbed, Fry turns to Farnsworth and tells him that Bender is playing too much D&D. Farnsworth warns Fry that if he doesn't confront Bender over this matter soon, Bender will completely lose his mind. By the time Fry does, it appears too late, and "Titanius" leaps into the city, attempting to destroy everything in sight, as well as stealing a bodyfull of dark matter from Nibbler's litter box as treasure.

At dinner with her parents, Leela shows Zoidberg that there is no problem with her relationship with them; however, they support the idea of the shock collar so she can control her temper. Fry comes into the house to warn them about Bender when he breaks in to terrorize them. Leela is unable to fight "Titanius" with her collar, so Fry "casts" a "Cone of Coldness" on him, duping him into believing he is frozen. Subdued, Bender is sent to the HAL Institute.

As Bender is being treated for his inability to distinguish fantasy from reality, Farnsworth watches the news with contempt as Mom is interviewed about the recent dark matter shortage. She explains that she has been investing so heavily on her dark matter mine in Alaska that she claims to be losing money, despite having made record profits last quarter. As it turns out, there is no shortage; it is all a ploy Mom is using to boost her fortunes on heightened prices.

With the crew curious as to why the Professor is so upset about the ordeal, the Professor reveals that while he was working for Mom for the third time (having twice realized how evil she is and vowing never to work for her again), he was experimenting with dark matter which, at the time, was a completely useless substance. Placing several balls in a particle accelerator, the experiment produced a red, glowing energy crystal which turned all dark matter in existence into fuel. He presented it to Mom, who promptly decided to get back together with her ex-husband Wernstrom and took the crystal for herself, firing Farnsworth. Farnsworth adds that, at the same time as the energy crystal, he produced an opposite crystal which he kept hidden from Mom. He explains that if the two crystals should come in close-enough range with each other, their effects on dark matter would negate, rendering dark matter useless and allowing scientists to care enough to produce new fuel, as well as ruining Mom's dark matter empire. However, he now believes the anti-crystal to be lost forever, little realizing that it was found and is currently being used by Cubert and Dwight as a 12-sided die in their D&D game.

Farnsworth develops a method that will allow him to locate the missing anti-crystal: he has invented a device that causes the crystal to emit a foul odor, allowing him to sniff it out with his smelling aid. However, this ends up alerting the presence of the crystal to Mom's attention, since she had actually known about its existence for some time. Realizing what this could mean for her dark matter empire, she sends her sons Walt, Larry, and Igner to the Planet Express building to obtain it.

Disguising themselves as owl exterminators, Walt, Larry, and Igner bumble their way through locating the anti-crystal while the kids are using it. Farnsworth, who is not convinced by their moronic display, unleashes an owl after them, exposing their identities and allowing him to find the anti-crystal.

With the anti-crystal in his possession once more, Farnsworth, Fry, and Leela set out with it to Mom's dark matter mine to put an end to her plans. Mom places Walt and Larry in command of her army of killbots, claiming that Igner alone cannot be trusted. She decides to tell Walt and Larry a shocking truth about Igner she has never told anyone, which Igner overhears. Meanwhile, Bender, still believing himself to be Titanius Anglesmith, is unfazed by all methods of therapy and declared insane, scheduled to be lobotomized.

Under relentless fire from the killbots, the ship is shot down and crashes before it can make it past the mine's outer defenses; however, as it turns out, the crew was not on the ship to begin with, having used it as a decoy while they infiltrate the mine on foot. Narrowly avoiding waves of killbots sent after them, the crew enters the heart of the mine where they are shocked to discover countless Nibblonians defacating dark matter in cages. They realize that the facility isn't a mine, but a farm.

Inside the facility, the crew gets to the heart of the mine, which turns out to be a huge Nibblonian farm, whom are force feed with chickens constantly to produce dark matter. Nibbler recalls what happened on Vergon 6, with the DOOP mine crew hiring Mom to mine the planet hollow, unfortunately, Mom captures all of the Nibblonians having learnt the secret of where dark matter comes from. After being escorted by Igner, the crew manages to get into Mom's control room, where Farnsworth is very close at getting the crystals to touch, but fails.

Meanwhile, Bender's therapy is not working, and Dr. Perceptron decides to put him down. As the crystals have made all dark matter glow, Bender's imagination along with the power of crystals sends him to Cornwood. At the facility, Farnsworth swallows the crystal to avoid Mom from getting it, but while she is ordering her sons to obtain the crystal from his stomach, Bender's waves reaches them sending them to Cornwood as well.

In the alternative reality, Fry emerges as himself, Leela, however, has turned into a centaur. Bender, as Titanius Anglesmith, rides to greet them to Cornwood.

At a party at Titanius's castle, he names Fry and Leela, Frydo and Leegola respectively. Calculon arrives to inform Titanius of dark knights approaching.

They ride out to defend themselves. But it is then they discover that Frydo has been carrying the Die of Power all this time, he rolls it on accident, it rolls 7, which in Appendix G, is "Banish Foes", which is done. Knowing the Die's power, they ride to Greyfarn who tells them the story of Momon who forges the Dies of Power in the plastic. But the Die's power is too great, and must be destroyed in the very same heat from which it was forged.

And thus they ride out, on their way they meet a group of centaurs, led by Hermaphrodite (Hermes), who, as his name suggests, is a hermaphrodite. To Leegola's disappointment, despite being master archers, the centaurs are pacifists. Hermaphrodite refuses to let the group pass, but he is such a wimp, they go through anyway.

After a long trip, they finally make their way into Cave of Hopelessness, in the hope of getting around Momon's forces, where they pick up Gynecaladriel (Amy), 'Queen of the Water Nymphos'. Inside they fight their way past a marauding band of 'Morcs' and have an encounter with the being of Zoidberg, which they confuse for the Tunneling Horror, the reason the Cave of Hopelessness gets its name. Leegola butchers Zoidberg in cold blood, only to discover he isn't the Tunneling Horror... the real Tunneling Horror is then revealed.

Realizing that Zoidberg was an innocent creature she killed, Leegola storms off weeping, and swearing never to hurt a living being again, though managing cutting Zoidberg's head off in the progress. At the centaurs dwelling, she asks to learn of their ways.

Meanwhile, the actual Tunnelling Horror shows up. Frydo is the only one not busy by something else (as Greyfarn and Gynaecaladrial are making out and Titanius is being beaten by the Tunnelling Horror), he attempts to throw everything in his pockets at it, but throws the Die of Power in the progress, which rolls 3, and he grows big enough to destroy the Tunnelling Horror, after which he shrinks down again and finally becoming seduced by the die's power, taking on a Gollum-like character.

At the feet of Momon's armies, the fellowship decides to go to Wipe Castle the next day to gather an army.

During the night, Frydo or Frollum (or Freedle, for what it matters) finally loses himself and tries to kill Titanius. Fortunately, he was lying in Gynecaladriel's bag, and Frydo is discovered before he can hurt anyone, at which he runs off for himself. Momon, finding out about their plan, orders all her forces to Wipe Castle.

The rest of the fellowship finally reaches Wipe Castle, where they found out that the king has sent the entire Royal Army to their death.

The Army of Momon finally arrives at Wipe Castle, in an epic, yet one-sided struggle. Wipe Castle remains some resistance, with Titanius, Gynaecaladrial and Greyfarn each using their own methods to fight off the attackers. Meanwhile, the centaurs having noticed the war, calls for an act from their leaders.

Leegola manages to convince the centaurs to act, (when Hermaphrodite challenges her to debate, Leegola beats the crap out of him and leads the centaurs to war, though he insists that he won) and their skilled archery saves the day against Momon's army and rescues Wipe Castle (as a reward, Gynaecaladrial kisses her, but it swiftly gets more and more passionate). Meanwhile, Frydo finally reaches to The Geysers of Gygax with the help of Zoidberg's head. Having noticed the effect on the world, the fellowship decides to ride out to help Frydo with destroying the Die of Power (but not until they're finished watching Leegola and Gynaecaladrial make out).

But at Momon's cave, Frydo cannot get himself to throw the Die in, having become seduced by its power. Zoidberg bites him on the butt, causing him to drop the Die, rolling it. Momon reacts by turning into a dragon, while Frydo rolls 12, "Mirror Mania", to which he becomes a dragon as well. While battling, the rest of the gang shows up. Frydo and Momon defeat each other out by injuring each other's soft underbelly (a dragon's one weakness).

The rest of the fellowship have become trapped because of the fragile staircases Momon destroyed. Ignis decides to help them on a giant bug, but Greyfarn becomes annoyed because Ignis cannot see it is a spider, not a bug due to the amount of legs. In anger he ignites his staff, and Ignis pulls out a lightsaber. They battle, until Ignis explains that Greyfarn is actually his father. Learning this, Greyfarn falls over the staircase and lands over Zoidberg who had obtained the Die, letting it roll into Momon's hands, who finally finishes everything off.

Through the same hole, the crew all winds up in their own regular crazy world, where Farnsworth explains Bender's wild imagination created an alternative reality for them all. But before Mom can retrieve the crystal, Farnsworth asks for the request of hugging his son, Igner. While hugging, Igner reveals that he swallowed the other crystal, allowing the crystals coming close enough together to render all dark matter useless. Farnsworth then reveals his alternative fuel source; Nibbler Power! Which is basically strapping a chick to a stick, and letting Nibblonians follow it, dragging the ship.